In conventional ring binders, the ring binder mechanism, i.e. the loose-leaf retaining device, is secured to a base member. The ring binder mechanism includes an elongate body portion comprising a curved upper casing supporting a pair of plates, and two rivets engaged with the upper casing, so as to prevent relative movement between the rivets and the upper casing. In particular, the rivet includes a post whose free end is deformable to engage with the upper casing. The plates are pivotable to selectively open or close several pairs of half-rings. The rivets may also be secured to the base member. The ring binder mechanism may thus be secured to the base member via the rivets, whereby relative movement between the ring binder mechanism and the base member is prevented.
Various ways have been proposed to enhance the engagement between the rivets and the upper casing, and thus the body portion, of the ring binder mechanism, so as to enhance the durability of the ring binder. It has, for example, been proposed to deform the free end of the post of the rivet such that it engages with both the upper surface and the lower surface of the upper casing. However, the force for effecting such an engagement between the post of the rivet and the upper casing will be relatively large, and may cause undesirable deformations at certain other locations of the rivet, e.g. the post.
It is thus an object of the present invention to provide a ring binder mechanism, and a ring binder, in which the above shortcoming is mitigated, or at least to provide a useful alternative to the public.